Optical modulating device having gate structure

ABSTRACT

An optical modulating device includes a permittivity change layer having a variable permittivity, a dielectric layer disposed on the permittivity change layer, a nanoantenna disposed on the dielectric layer, and a light-emitting structure disposed adjacent to the permittivity change layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/214,919, filed on Jul. 20, 2016, which claims the benefit of U.S.Provisional Patent Application No. 62/197,331, filed on Jul. 27, 2015 inthe U.S. Patent and Trademark Office, and priority from Korean PatentApplication No. 10-2016-0007548, filed on Jan. 21, 2016 in the KoreanIntellectual Property Office, the disclosures of which are incorporatedherein by reference in their entireties.

BACKGROUND 1. Field

Apparatuses consistent with exemplary embodiments relate to opticaldevices for modulating light.

2. Description of the Related Art

Optical devices for modulating transmittance/reflection, polarization,phase, intensity, optical path, etc. of incident light are used invarious optical apparatuses. Also, optical modulators of variousstructures are provided to control the properties described above in anoptical system in a desired manner.

For example, structures such as liquid crystals having opticalanisotropy, a microelectromechanical system (MEMS) using minutemechanical motion of an optical shielding/reflecting element, etc. arewidely implemented in general optical modulators. These general opticalmodulators have a slow operational response rate of several μs, due tocharacteristics of driving methods thereof.

There have been attempts to implement a nanoantenna using surfaceplasmon resonance occurring at a boundary between a metal layer and adielectric layer, in optical devices.

SUMMARY

Exemplary embodiments may address at least the above problems and/ordisadvantages and other disadvantages not described above. Also, theexemplary embodiments are not required to overcome the disadvantagesdescribed above, and may not overcome any of the problems describedabove.

Exemplary embodiments provide optical devices for modulating light.

According to an aspect of an exemplary embodiment, there is provided anoptical modulating device including a permittivity change layer having avariable permittivity, a dielectric layer disposed on the permittivitychange layer, a nanoantenna disposed on the dielectric layer, and alight-emitting structure disposed adjacent to the permittivity changelayer.

The light-emitting structure may be configured to emit light having agreater wavelength than light incident on the light-emitting structurein response to the incident light, as an excitation source.

The light-emitting structure may include light-emitting particles.

The optical modulating device may further include an insulating materiallayer on which the permittivity change layer is disposed, thelight-emitting particles being embedded in the insulating materiallayer.

The light-emitting structure may include a semiconductor quantum well ora semiconductor PN junction.

The optical modulating device may further include a metal layer on whichthe light-emitting structure, the permittivity change layer, thedielectric layer, and the nanoantenna are sequentially disposed.

The optical modulating device may further include a voltage-applierconfigured to apply a voltage between the permittivity change layer andthe nanoantenna.

The permittivity change layer may include an active area in which acarrier concentration changes based on the applied voltage.

The permittivity change layer may include a transparent conductiveoxide.

An optical apparatus may include the optical modulating device.

According to an aspect of another exemplary embodiment, there isprovided an optical modulating device including a substrate,nanoantennas disposed on the substrate and spaced apart from oneanother, a dielectric layer disposed on the nanoantennas, a permittivitychange layer disposed on the dielectric layer and having a variablepermittivity, and a light-emitting structure disposed on thepermittivity change layer and between the nanoantennas.

The light-emitting structure may be configured to emit light having agreater wavelength than light incident on the light-emitting structurein response to the incident light, as an excitation source.

The light-emitting structure may include light-emitting particles.

The optical modulating device may further include an insulating materiallayer disposed on the permittivity change layer, the light-emittingparticles being embedded in the insulating material layer.

The light-emitting structure may include a semiconductor quantum well ora semiconductor PN junction.

The optical modulating device may further include an insulating materiallayer covering the permittivity change layer and the light-emittingstructure.

The optical modulating device may further include voltage-appliersconfigured to apply respective voltages between the respectivenanoantennas and the permittivity change layer.

The permittivity change layer may include a transparent conductiveoxide.

An optical apparatus may include the optical modulating device, and abacklight configured to provide light to the optical modulating device.

The optical apparatus may further include a driving circuit disposed onthe substrate and configured to control voltages applied to therespective nanoantennas.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will be more apparent by describingexemplary embodiments with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a schematic structure of an opticalmodulating device according to an exemplary embodiment;

FIG. 2 is a cross-sectional view taken along a line A-A′ of the opticalmodulating device of FIG. 1;

FIG. 3 is a graph obtained by computer simulation with respect to achange of permittivity in the optical modulating device of FIG. 1,according to a carrier concentration of a permittivity change layer;

FIG. 4 is a graph obtained by computer simulation with respect toreflectivity in the optical modulating device of FIG. 1, according to avoltage applied to a permittivity change layer and wavelengths ofincident light;

FIG. 5 is a graph obtained by computer simulation with respect to aphase change in the optical modulating device of FIG. 1, according to avoltage applied to a permittivity change layer and wavelengths ofincident light;

FIG. 6 is a graph obtained by computer simulation with respect to achange of local density of optical states (LDOS) in the opticalmodulating device of FIG. 1, according to a voltage applied to apermittivity change layer and wavelengths of incident light, which isshown in comparison with comparative exemplary embodiments;

FIG. 7 is a graph obtained by computer simulation with respect to achange of LDOS in the optical modulating device of FIG. 1, according toa voltage applied to a permittivity change layer and wavelengths ofincident light;

FIG. 8 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment;

FIG. 9 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment;

FIG. 10 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment;

FIG. 11 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment;

FIG. 12 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment;

FIG. 13 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment;

FIG. 14 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment;

FIG. 15 is a cross-sectional view of a schematic structure of an opticalmodulating device according to another exemplary embodiment; and

FIG. 16 is a cross-sectional view of a schematic structure of an opticalapparatus according to an exemplary embodiment.

DETAILED DESCRIPTION

Exemplary embodiments are described in greater detail below withreference to the accompanying drawings.

In the following description, like drawing reference numerals are usedfor like elements, even in different drawings. The matters defined inthe description, such as detailed construction and elements, areprovided to assist in a comprehensive understanding of the exemplaryembodiments. However, it is apparent that the exemplary embodiments canbe practiced without those specifically defined matters. Also,well-known functions or constructions may not be described in detailbecause they would obscure the description with unnecessary detail.

In addition, the terms such as “unit,” “-er (-or),” and “module”described in the specification refer to an element for performing atleast one function or operation, and may be implemented in hardware,software, or the combination of hardware and software.

FIG. 1 is a perspective view of a schematic structure of an opticalmodulating device 100 according to an exemplary embodiment. FIG. 2 is across-sectional view taken along a line A-A′ of the optical modulatingdevice 100 of FIG. 1.

Referring to FIGS. 1 and 2, the optical modulating device 100 includes apermittivity change layer 140 having a variable permittivity, adielectric layer 150 disposed on the permittivity change layer 140, ananoantenna NA disposed on the dielectric layer 150, and alight-emitting structure 120 disposed adjacent to the permittivitychange layer 140.

The optical modulating device 100 further includes an insulatingmaterial layer 130, and the light-emitting structure 120 is embedded inthe insulating material layer 130 and is disposed under the permittivitychange layer 140.

Also, the optical modulating device 100 further includes a metal layer110 disposed under the permittivity change layer 140. On the metal layer110, the insulating material layer 130 in which the light-emittingstructure 120 is embedded, the permittivity change layer 140, thedielectric layer 150, and the nanoantenna NA are sequentially disposed.

The permittivity change layer 140 may include a material having anoptical property that changes in response to an external signal. Theexternal signal may be an electrical signal. The permittivity changelayer 140 may include transparent conductive oxide (TCO), such as indiumtin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO),gallium zinc oxide (GZO), aluminum gallium zinc oxide (AGZO), andgallium indium zinc oxide (GIZO). Also, the permittivity change layer140 may include transition metal nitride, such as TiN, ZrN, HfN, andTaN. In addition, the permittivity change layer 140 may include anelectro-optic material, a valid permittivity of which changes when anelectrical signal is applied, such as LiNbO₃, LiTaO₃, potassiumtantalate niobate (KTN), and lead zirconate titanate (PZT). Further, thepermittivity change layer 140 may include various polymer materialshaving an electro-optic property.

A voltage applier 190 for applying a voltage between the permittivitychange layer 140 and the nanoantenna NA is included in the opticalmodulating device 100. Hereinafter, it will be described that thepermittivity change layer 140 includes a material, a permittivity ofwhich changes according to an electrical signal. However, thepermittivity change layer 140 is not limited thereto. For example, thepermittivity change layer 140 may include a material, a permittivity ofwhich changes due to phase transition occurring at a temperature that isequal to or higher than a predetermined temperature when heat is appliedthereto. For example, the permittivity change layer 140 may include VO₂,VO₂O₃, EuO, MnO, CoO, CoO₂, LiCoO₂, Ca₂RuO₄, or the like.

The nanoantenna NA includes a conductive material, is an artificialstructure having a shape with dimension of a sub-wavelength, andintensely gathers light in a predetermined wavelength band. Here, thesub-wavelength denotes a wavelength of a smaller dimension than anoperation wavelength of the nanoantenna NA, that is, the predeterminedwavelength described above. Any dimension forming a shape of thenanoantenna NA, for example, at least one among a thickness, a width, aheight, and a gap between the nanoantennas NAs may correspond to thedimension of the sub-wavelength.

The above-described function of the nanoantenna NA is known to bepossible by surface plasmon resonance occurring at a boundary between ametal material and a dielectric material, and a resonance wavelengthvaries depending on a detailed shape of the nanoantenna NA. Hereinafter,the nanoantenna NA, the dielectric layer 150, and an interface at whichsurface plasmon resonance occurs will be called a “metasurface.”

It is illustrated that a cross-sectional shape of the nanoantenna NA iscross-shaped. However, it is not limited thereto. For example, thecross-sectional shape of the nanoantenna NA may be circle-shaped,star-shaped, or polygon-shaped.

The conductive material included in the nanoantenna NA may include ametal material having high conductivity, at which surface plasmonexcitation may occur. For example, the conductive material may includeat least one selected from Cu, Al, Ni, Fe, Co, Zn, Ti, Ru, Rh, Pd, Pt,Ag, Os, Ir, Pt, and Au, or may include an alloy including any one amongCu, Al, Ni, Fe, Co, Zn, Ti, Ru, Rh, Pd, Pt, Ag, Os, Ir, Pt, and Au.Also, the conductive material may include a two-dimensional materialhaving high conductivity, such as graphene, or conductive oxide.

The dielectric layer 150 may include a material, such as Al₂O₃, HfO₂,MgO, or SiO₂.

The light-emitting structure 120 may include various materials havingphotoluminescence. For example, the light-emitting structure 120 mayinclude, as light-emitting particles, any one among rare earth ions,quantum dots, plasmonic nanoparticles, dielectric nanoparticles, andsemiconductor nanoparticles. For example, the light-emitting particlesmay include any one among Si-based nanocrystals, groups II-VI basedcompound semiconductor nanocrystals, groups III-V based compoundsemiconductor nanocrystals, groups IV-VI based compound semiconductornanocrystals, and a mixture thereof. The groups II-VI based compoundsemiconductor nanocrystals may include any one selected from the groupconsisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS,CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS,CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HggZnTe, CdZnSeS,CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, andHgZnSTe. The groups III-V based compound semiconductor nanocrystals mayinclude any one selected from the group consisting of GaN, GaP, GaAs,AlN, AlP, AlAs, InN, InP, InAs, GaNP, GaNAs, GaPAs, AlNP, AlNAs, AlPAs,InNP, InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs,InAlNP, InAlNAs, and InAlPAs. The groups IV-VI based compoundsemiconductor nanocrystals may include SbTe.

FIG. 2 illustrates the light-emitting structure 120 as thelight-emitting particles. However, the light-emitting structure 120 isnot limited thereto, and may include a PN junction structure or aquantum well structure.

The metal layer 110 may function as a mirror layer for reflecting light.According to the provision of the metal layer 110, directions ofincident light (Li), and modulated light (Lm) are formed, as illustratedin FIG. 2. The metal layer 110 may include various metal materialscapable of performing this function. For example, the metal layer 110may include at least one selected from Cu, Al, Ni, Fe, Co, Zn, Ti, Ru,Rh, Pd, Pt, Ag, Os, Ir, Pt, and Au.

When the metal layer 110 is provided, a voltage may be applied betweenthe nanoantenna NA and the metal layer 110, according to necessity.

Referring to FIG. 2, the permittivity change layer 140 includes anactive area 145, in which a carrier concentration changes according towhether or not a voltage is applied between the permittivity changelayer 140 and the nanoantenna NA. The active area 145 is formed in thepermittivity change layer 140 to be adjacent to the dielectric layer150, and has the carrier concentration that changes according to theapplied voltage. According to the carrier concentration formed in theactive area 145, a shape of modulation of light that is incident in thelight modulating device 100 may be adjusted. In this respect, the activearea 145 may be understood as a gate adjusting and controlling theoptical modulation performance of the nanoantenna NA.

A permittivity of the permittivity change layer 140 varies according toa wavelength. Relative permittivity (ε_(r)) to vacuum permittivity (ε₀)is called a dielectric constant, and the real part of the dielectricconstant of the permittivity change layer 140 is 0 in a wavelength band.

A wavelength band in which the real part of the dielectric constant hasa value that is 0 or very adjacent to 0 is called an epsilon near zero(ENZ) wavelength band. A dielectric constant of most of materials isrepresented as a function of a wavelength, and may be represented as acomplex number. A vacuum dielectric constant is 1, and in the case of ageneral dielectric material, the real part of the dielectric constant isa positive number that is greater than 1. In the case of a metal, thereal part of the dielectric constant may be a negative number. In mostwavelength bands, the dielectric constant of most of materials has avalue that is greater than 1, while in a wavelength band, the real partof the dielectric constant may have a value that is 0.

When the real part of the dielectric constant has a value that is 0 oris very adjacent to 0, it is known that an optical property appears, andthe optical modulating device 100 according to an exemplary embodimentmay set an operational wavelength band as an area including the ENZwavelength band of the permittivity change layer 140. That is, bysetting a resonance wavelength band of the nanoantenna NA similar to theENZ wavelength band of the permittivity change layer 140, a range withinwhich the optical modulation performance may be adjusted by an appliedvoltage may be increased.

The ENZ wavelength band of the permittivity change layer 140 variesaccording to a carrier concentration formed in the active area 145. Toutilize the ENZ wavelength band of the permittivity change layer 140, arange of a voltage in which the voltage applier 190 applies between thepermittivity change layer 140 and the nanoatenna NA may include avoltage value with which a resonance wavelength of a plasmonicnanoantenna layer 170 is consistent with a wavelength in which thepermittivity change layer 140 has an ENZ property.

The light-emitting structure 120 may emit, as an excitation source,light having a greater wavelength than incident light, by being excitedby the incident light. A dipole emitter formed in the light-emittingstructure 120 by excitation light is coupled to a gap plasmon mode in aresonance wavelength band of the metasurface. That is, electromagneticenergy radiated by the dipole emitter is transmitted to a far-field viaa resonance mode of the nanoantenna NA, and radiation power is relatedto local density of optical states (LDOS). The LDOS is related to adecay rate of the dipole emitter, and may be represented as the numberof photons emitted per unit time. As the LDOS increases, the radiationpower increases. The LDOS may be controlled by a change of permittivityof the permittivity change layer 140. A complex refractivity changelocally occurring in the permittivity change layer 140 contributes tocontrol of the LDOS. That is, it is analyzed that a degree of thecoupling of the dipole emitter and the plasmon may be adjusted dependingon a degree of accumulation or depletion of charges in the active area145 formed in the permittivity change layer 140. The coupling efficiencymay be adjusted according to an applied voltage. Also, via this, arelative coupling efficiency of the dipole emitter and the nanoantennaNA may be adjusted. Also, when the nanoantenna NA has directivity, lightmay be adjusted to be emitted in a desired direction.

As described above, the incident light (Li) to the optical modulatingdevice 100 is emitted as modulated light (Lm), and a wavelength, anintensity, a phase, a direction, etc. of the modulated light (Lm) may beadjusted according to the described elements.

FIG. 3 is a graph obtained by computer simulation with respect to achange of permittivity according to a carrier concentration of thepermittivity change layer 140, in the optical modulating device 100 ofFIG. 1.

In the graph, a horizontal axis indicates a location in the permittivitychange layer 140 as a distance from a boundary surface between thepermittivity change layer 140 and the dielectric layer 150. A verticalaxis indicates a value of a real number of a permittivity RE.

A unit of the carrier concentration is cm⁻³, and the graph shows achange in the real part of the permittivity based on three types ofcarrier concentrations.

FIG. 4 is a graph obtained by computer simulation with respect toreflectivity according to a voltage applied to the permittivity changelayer 140 and wavelengths of incident light, in the optical modulatingdevice 100 of FIG. 1.

A wavelength band in which the reflectivity becomes the smallest is aresonance wavelength band, and it is shown that the reflectivity changesand the resonance wavelength band is adjusted, according to the appliedvoltage.

FIG. 5 is a graph obtained by computer simulation with respect to aphase change in the optical modulating device 100 of FIG. 1, accordingto a voltage applied to the permittivity change layer 140 andwavelengths of incident light

It is shown in the graph that the phase change is adjusted according toadjustment of the applied voltage, and the phase change within a rangethat is proximate to about 27 is possible.

FIG. 6 is a graph obtained by computer simulation respect to a change ofLDOS according to a voltage applied to the permittivity change layer 140and wavelengths of incident light, in the optical modulating device 100of FIG. 1, shown in comparison with comparative exemplary embodiments.

In the graph, an exemplary embodiment 1V is the case in which theapplied voltage is 1V, an exemplary embodiment 5V is the case in whichthe applied voltage is 5V. A first comparative exemplary embodiment hasa structure, in which only the nanoantenna NA and the light-emittingstructure 120 are provided in the optical modulating device 100 of FIG.1, a second comparative exemplary embodiment includes only a lower metallayer 11 and the light-emitting structure 120 in the optical modulatingdevice 100, and a third comparative exemplary embodiment has a structurein which the permittivity change layer 140 is not provided in theoptical modulating device 100.

In the graph, a vertical axis indicates an LDOS, a subscript z denotesthat a dipole direction is computer simulated as a z direction.

Referring to the graph, it is shown that a resonance wavelength band isformed and a level of the LDOS increases, when a metasurface structureis provided. It is also shown that the LDOS may be changed according toadjustment of a complex refractivity by the applied voltage, inexemplary embodiments in which the permittivity change layer 140 isprovided.

FIG. 7 is a graph obtained by computer simulation with respect to achange of LDOS according to a voltage applied to the permittivity changelayer 140 and wavelengths of incident light, in the optical modulatingdevice 100 of FIG. 1.

The graph shows that the LDOS may be adjusted by varying the voltageapplied to the permittivity change layer 140.

FIG. 8 is a cross-sectional view of a schematic structure of an opticalmodulating device 101 according to another exemplary embodiment.

The optical modulating device 101 differs from the optical modulatingdevice 100 of FIG. 1 in that the optical modulating device 101implements a PN junction structure as a light-emitting structure 121.

The optical modulating device 101 includes the metal layer 110, theinsulating material layer 130 in which the light-emitting structure 121is included, the permittivity change layer 140 in which the active area145 is included, the dielectric layer 150, and the nanoantenna NA.

The light-emitting structure 121 includes the semiconductor PN junctionstructure in which a p-type semiconductor layer 121 a and an n-typesemiconductor layer 121 b are adjoined to each other. An emitter isformed when electrons and holes are combined at an interface of the PNjunction by incident optical energy. Coupling of the emitter and asurface plasmon is controlled by a change of complex permittivity of thepermittivity change layer 140 and an LDOS is adjusted.

FIG. 9 is a cross-sectional view of a schematic structure of an opticalmodulating device 102 according to another exemplary embodiment.

The optical modulating device 102 differs from the optical modulatingdevice 100 of FIG. 1 in that the optical modulating device 102implements a semiconductor quantum well structure as a light-emittingstructure 122.

The optical modulating device 102 includes the metal layer 110, theinsulating material layer 130 in which the light-emitting structure 122is included, the permittivity change layer 140 in which the active area145 is included, the dielectric layer 150, and the nanoantenna NA.

The light-emitting structure 122 may include a plurality ofsemiconductor layers having different thicknesses and compositions. Forexample, the light-emitting structure 122 includes a structure in whicha well layer 122 b is interposed between two barrier layers 122 a and122 c. In FIG. 9, it is illustrated as a single quantum well (SQW)structure in which the well layer 122 b is interposed between the twobarrier layers 122 a and 122 c. However, it is only exemplary, and thelight-emitting structure 122 is not limited thereto. The light-emittingstructure 122 may include a multi-quantum well (MQW) structure in whichbarrier layers and well layers are repeatedly stacked. The well layer122 b, and the barrier layers 122 a and 122 c may include group IIInitride semiconductor materials. For example, the barrier layers 122 aand 122 c may include InGaN or GaN, and the well layer 122 b may includeInGaN. However, it is not limited thereto. The well layer 122 b includesa material having a less energy band gap than a material of the barrierlayers 122 a and 122 c. The barrier layers 122 a and 122 c may be dopedwith an n-type or p-type material, and it is also possible that both ofthe well layer 122 b and the barrier layers 122 a and 122 c are doped.

Electrons and holes are generated when incident optical energy isabsorbed in the barrier layers 122 a and 122 c. The generated electronsand holes move to the well layer 122 b, are confined in the well layer122 b and combined with each other. The combination of the electrons andholes occurring in the well layer 122 b serves a as an emitter. Couplingof the emitter and a surface plasmon is controlled by a change ofcomplex permittivity of the permittivity change layer 140 and an LDOS isadjusted. When the LDOS increases, an amount of light emissionincreases, and when the LDOS decreases, an amount of light emissiondecreases.

FIG. 10 is a cross-sectional view of a schematic structure of an opticalmodulating device 103 according to another exemplary embodiment.

The optical modulating device 103 has a transmittance-type structure.That is, incident light (Li) is transmitted through the opticalmodulating device 103 and is emitted as modulated light (Lm).

The optical modulating device 103 includes the insulating material layer130 in which the light-emitting structure 120 is embedded, thepermittivity change layer 140 in which the active area 145 is included,the dielectric layer 150, and the nanoantenna NA. The optical modulatingdevice 103 differs from the optical modulating device 100 of FIG. 1 inthat optical modulating device 103 does not include the metal layer 110of FIG. 1.

FIG. 11 is a cross-sectional view of a schematic structure of an opticalmodulating device 104 according to another exemplary embodiment.

The optical modulating device 104 is also the transmittance type as theoptical modulating device 103 of FIG. 10. However, the opticalmodulating device 104 differs from the optical modulating device 103 ofFIG. 10 in that the optical modulating device 104 implements asemiconductor PN junction structure as the light-emitting structure 121.

FIG. 12 is a cross-sectional view of a schematic structure of an opticalmodulating device 105 according to another exemplary embodiment.

The optical modulating device 105 is also the transmittance type as theoptical modulating device 103 of FIG. 10. However, the opticalmodulating device 105 differs from the optical modulating device 103 ofFIG. 10 in that the optical modulating device 105 implements asemiconductor quantum well structure as the light-emitting structure122.

FIG. 13 is a cross-sectional view of a schematic structure of an opticalmodulating device 106 according to another exemplary embodiment.

The optical modulating device 106 includes a substrate 105, a pluralityof nanoantennas NA1 and NA2 disposed on the substrate 105 to be adjacentto one another, a dielectric layer 151 disposed on the plurality ofnanoantennas NA1 and NA2, a permittivity change layer 141 disposed on adielectric layer 151 and having a variable permittivity, and thelight-emitting structure 120 disposed on the permittivity change layer141 between the plurality of nanoantennas NA1 and NA2.

The light-emitting structure 120 may include light-emitting particlesand is embedded in the insulating material layer 130 on the permittivitychange layer 140, as illustrated in FIG. 13.

The optical modulating device 106 further includes voltage appliers 191and 192 for separately applying voltages between each of the pluralityof nanoantennas NA1 and NA2, and the permittivity change layer 141. Forexample, the permittivity change layer 141 may be applied with a groundvoltage, and a different voltage may be applied to each of the pluralityof nanoantennas NA1 and NA2.

The light-emitting structure 120 disposed between the plurality ofnanoantennas NA1 and NA2 may be coupled to a surface plasmon, in arespectively different coupling strength, based on the adjacentnanoantennas NA1 and NA2. An LDOS in the location of the light-emittingstructure 120 may be determined by the combination of the couplingstate.

FIG. 14 is a cross-sectional view of a schematic structure of an opticalmodulating device 107 according to another exemplary embodiment.

The optical modulating device 107 differs from the optical modulatingdevice 106 of FIG. 13 in that the optical modulating device 107implements a PN junction structure as the light-emitting structure 121.

FIG. 15 is a cross-sectional view of a schematic structure of an opticalmodulating device 108 according to another exemplary embodiment.

The optical modulating device 108 differs from the optical modulatingdevice 106 of FIG. 13 in that the optical modulating device 108 asemiconductor quantum well structure as the light-emitting structure122.

FIG. 16 is a cross-sectional view of a schematic structure of an opticalapparatus 1000 according to an exemplary embodiment.

The optical apparatus 1000 includes a backlight 1100 and an opticalmodulating device 1700.

The optical modulating device 1700 includes a plurality of nanoantennasNA1, NA2, NA3, and NA4 disposed on a substrate 1105 to be apart from oneanother. The substrate 1105 may be a transparent substrate.Alternatively, the substrate 1105 may at least have a transparentcharacteristic with respect to light of a wavelength band provided bythe backlight 1100.

A dielectric layer 1500 and a permittivity change layer 1400 aredisposed on the plurality of nanoantennas NA1, NA2, NA3, and NA4. Thedielectric layer 1500 and the permittivity change layer 1400 are formedalong surfaces of the plurality of nanoantennas NA1, NA2, NA3, and NA4,and grooved areas may be formed between the plurality of nanoantennasNA1, NA2, NA3, and NA4. Light-emitting structures 1211, 1212, and 1213are disposed in these grooved areas. The optical modulating device 1700further includes an insulating material layer 1300 covering thedielectric change layer 1400, and the light-emitting structures 1211,1212, and 1213 are embedded in the insulating material layer 1300. Adriving circuit 1110 for controlling voltages applied to the pluralityof nanoantennas NA1, NA2, NA3, and NA4, respectively, is furtherdisposed on the substrate 1105.

The backlight 1100 provides light that is to be modulated in the opticalmodulating device 1700. The light provided by the backlight 1100 maysupply optical energy to the light-emitting structures 1211, 1212, and1213 provided in the optical modulating device 1700, and may generate anemitter. The backlight 1100 may provide ultraviolet light (UV) or lightof a blue color. A light-emitting wavelength in the light-emittingstructures 1211, 1212, and 1213 is greater than a wavelength of thelight provided by the backlight 1100. Light-emitting power of theemitter generated in each of the light-emitting structures 1211, 1212,and 1213 is determined by an LDOS formed according to a change ofpermittivity of the permittivity change layer 1400 of the opticalmodulating device 1700. The change of permittivity may be controlled byan applied voltage.

The optical apparatus 1000 further includes a controller 1800 toseparately control voltages applied between each of the plurality ofnanoantennas NA1, NA2, NA3, and NA4 and the permittivity change layer1400. Accordingly, the light-emitting structure 1211 between thenanoantennas NA1 and NA2, the light-emitting structure 1212 between thenanoantennas NA2 and NA3, and the light-emitting structure 1213 betweenthe nanoantennas NA3 and NA4 may indicate different LDOSs and may serveas separate pixels that are separately controlled.

The optical apparatus 1000 may serve as a display apparatus. To thisend, sizes and materials of light-emitting particles of thelight-emitting structures 1211, 1212, and 1213 may be adjusted such thatthe light-emitting structures 1211, 1212, and 1213 emit light ofdifferent wavelengths. Depending on image information that is to beformed, the controller 1800 may control the voltages between each of theplurality of nanoantennas NA1, NA2, NA3, and NA4 and the permittivitychange layer 1400 to control on/off of each of pixels to display theimage. The image formed as such may have high color purity, and thus,may represent improved color gamut and high contrast.

The optical apparatus 1000 may be used not only as the display apparatusbut also as other apparatuses. For example, the optical apparatus 1000may be used as a beam deflector or a beam shaper by forming theplurality of nanoantennas NA1, NA2, NA3, and NA4 as shapes havingdifferent directionalities, or giving rules to voltages applied thereto.

The light-emitting structures 1211, 1212, and 1213 are illustrated aslight-emitting particles. However, the light-emitting structures 1211,1212, and 1213 are not limited thereto. The semiconductor PN junctionstructure or the semiconductor quantum well structure illustrated inFIGS. 14 and 15, respectively, may be implemented as the light-emittingstructures 1211, 1212, and 1213. In addition, various materials andstructures having photoluminescence may be used as the light-emittingstructures 1211, 1212, and 1213.

It is illustrated that the optical modulating device 1700 of the opticalapparatus 1000 is realized by arraying the structure of FIG. 13.However, it is not limited thereto. For example, the optical modulatingdevice 1700 may be realized by repeatedly arraying the structure ofFIG. 1. In this case, the shape of the backlight 1100 may be changed tobe more appropriate for providing light to the light-emitting structures1211, 1212, and 1213.

The optical modulating devices 100 through 108 and 1700 described aboveinclude a nanoantenna NA, a permittivity change layer, and alight-emitting structure, and may modulate incident light as variousshapes by using an area in the permittivity change layer, in which acarrier concentration changes, as a gate.

Also, energy of the incident light is absorbed in the light-emittingstructure of the optical modulating device so that light of differentwavelengths may be emitted, and light-emitting energy may be controlledby adjusting a permittivity of the permittivity change layer.

The optical modulating devices 100 through 108 and 1700 may beminiaturized and high speed driving may be possible, and thus, theoptical modulating devices 100 through 108 and 1700 may be applied tovarious optical apparatuses to improve the performance of the opticalapparatuses.

The optical modulating devices 100 through 108 and 1700 may realize adisplay apparatus, together with a backlight, and may provide an imagehaving miniaturized pixels and improved contrast.

The foregoing exemplary embodiments are examples and are not to beconstrued as limiting. The present teaching can be readily applied toother types of apparatuses. Also, the description of the exemplaryembodiments is intended to be illustrative, and not to limit the scopeof the claims, and many alternatives, modifications, and variations willbe apparent to those skilled in the art.

What is claimed is:
 1. An optical modulating device comprising: anactive area in which a carrier concentration changes based on anelectric signal; a nanoantenna disposed adjacent to the active area; anda light-emitting structure disposed adjacent to the active area.
 2. Theoptical modulating device of claim 1, wherein the nanoantenna has ashape with dimension of sub-wavelength.
 3. The optical modulating deviceof claim 1, wherein the active area is included in a permittivity changelayer, permittivity of the permittivity change layer changing accordingto the electrical signal.
 4. The optical modulating device of claim 3,wherein the permittivity change layer comprises a transparent conductiveoxide.
 5. The optical modulating device of claim 1, wherein thelight-emitting structure is configured to emit light having a greaterwavelength than light incident on the light-emitting structure inresponse to the incident light, as an excitation source.
 6. The opticalmodulating device of claim 1, wherein the light-emitting structurecomprises light-emitting particles.
 7. The optical modulating device ofclaim 1, further comprising an insulating material layer on which theactive area is disposed, light-emitting particles being embedded in theinsulating material layer.
 8. The optical modulating device of claim 1,wherein the light-emitting structure comprises a semiconductor quantumwell or a semiconductor PN junction.
 9. The optical modulating device ofclaim 1, further comprising a metal layer on which the light-emittingstructure, the active area, and the nanoantenna are sequentiallydisposed.
 10. The optical modulating device of claim 1, furthercomprising a voltage-applier configured to apply the electric signal tothe active area.
 11. The optical modulating device of claim 1, furthercomprising a dielectric layer between the nanoantenna and the activearea.
 12. An optical apparatus comprising the optical modulating deviceof claim 1.